1. Field of the Invention
The present invention relates to an oil separator for blow-by gas, and more particularly, to an oil separator for trapping oil mist in blow-by gas generated in an engine crankcase of an internal combustion engine such as an automobile engine, the oil separator being structured so that multiple cones trap the oil mist.
2. Description of the Related Art
In an internal combustion engine such as an automobile engine, at a time of operation thereof, blow-by gas leaks out from a gap between a piston ring and a cylinder wall. Further, emission of the blow-by gas into the atmosphere causes air pollution. Accordingly, by using a so-called positive crankcase ventilation (PCV) system provided inside the internal combustion engine, the blow-by gas is returned to an intake system and then reburnt.
In this case, the blow-by gas contains oil mist, which is atomized lubricating oil such as engine oil. Therefore, the oil mist in the blow-by gas needs to be prevented from flowing out to the intake system. In this regard, as means for trapping the oil mist in the blow-by gas, there is provided an oil separator midstream of a connection channel for connecting an intake pipe line with a crankcase or inside of a cylinder head cover.
In the previous described cone type oil separator configuration, a range of a flow rate of the blow-by gas, in which a cone can exert the best performance, is limited. Another known oil separator has proposed a single cone in the oil separator, yet a problem arises such that the flow rate of the blow-by gas is low, resulting in a deteriorated trapping performance for the oil mist.
Also proposed is a multiple cone configuration instead of the single cone configuration. In this configuration, cones are downsized so as to generate swirling flow even when the flow rate of the blow-by gas is low, whereby making it possible to efficiently trap the oil mist. When the flow rate of the blow-by gas is high, the trapping operation for the oil mist can be divided by the multiple cones.
Yet, since this configuration needs to have multiple cones, each of which is capable of efficiently separating the oil mist, the structure needs to be simple enough to keep manufacturing cost low.
In this case, in order to achieve efficient trapping of the oil mist by each cone, it has been considered to include a configuration in which a flow channel dedicated for the blow-by gas is provided to each of the cones so as to cause the blow-by gas to flow into each cone from a tangential direction. However, this method makes this configuration complicated, and leads to cost increase.
On the other hand, a structure in which the flow channel is partitioned at positions directly before the blow-by gas flows into each cone to introduce the flow of the blow-by gas in parts into each of the cones has been proposed. The blow-by gas hits against partitions of the flow channel, and hence a flow is likely to be disturbed. Further, the flowing-in blow-by gas needs to be distributed to the cones which are arranged in parallel and separated from each other, and hence the flow-in port for the blow-by gas into the cones are formed to have a wide width. As a result, the blow-by gas flows directly also into the vicinity of the cone centers. Therefore, the oil separator according to this configuration has a structure disadvantageous for forming the swirling flow in the cones, and an oil mist trapping efficiency of the cones is low or inefficient.
Therefore, there has been a need in the art for an oil separator having a multiple cone configuration, which has a simple structure and high trapping efficiency for oil mist.